Mine positive pressure oxygen respirator full face mask double-layer lens anti-fog method and structure

Abstract

The invention discloses a double-layer lens anti-fog method and structure for a full face mask of a mining positive pressure oxygen respirator. The structure comprises a mask, the mask is composed of an outer-layer lens, an inner-layer lens, a flexible sealing frame, an upper hoop and a lower hoop, the outer-layer lens and the inner-layer lens are fixed in parallel through the sealing frame to form an interlayer, and the side wall of the interlayer is provided with an air inlet heat insulation pipeline and an air outlet; branch oxygen absorbs reaction heat of a CO2 absorbent through a spiral copper pipe of the cleaning tank, and enters an interlayer to heat an inner-layer lens after being heated, so that the temperature is higher than a dew point, and the discharged oxygen is converged into a closed cycle. According to the method, branch oxygen (accounting for 20%-30% of the total flow) is heated to 35 DEG C or above, airflow replacement (5-10 times per minute) is achieved in combination with a flow guide plate, the positive pressure of an interlayer is maintained, and cold condensation fog is prevented. The self heat source of equipment is utilized, external energy is not needed, the anti-fog effect is lasting, the total light transmittance of the mask is larger than or equal to 86%, the mask adapts to the mine low-temperature and high-humidity environment, the rescue efficiency is improved, and the intrinsic safety requirement is met.

Description

Technical Field

[0001] This invention belongs to the field of respiratory protection technology, specifically relating to a method and structure for preventing fogging with double-layer lenses on a full-face mask of a positive pressure oxygen respirator for mining. Background Technology

[0002] In the hazardous working environment of underground mines, positive pressure oxygen respirators are core personal protective equipment for ensuring the safety of mine rescue workers. The full-face mask, as a key component, bears the dual responsibility of providing clear vision and reliable respiratory isolation. However, due to the generally low temperatures in mines, typically between 5°C and 20°C, and the high temperature and humidity of exhaled air (approximately 37°C, relative humidity above 90%), a significant temperature difference exists between the inside of the mask and the outside. Under these conditions, the surface temperature of the inner lens easily drops below the dew point, causing water vapor to condense into fog, severely affecting the user's vision and threatening operational safety. For example, during mine rescue operations, blurred vision may prevent rescue workers from accurately identifying collapse risks, gas leaks, or the location of injured personnel, leading to secondary accidents, casualties, and property damage.

[0003] In existing technologies, the full-face masks of positive pressure oxygen respirators typically employ a single-layer optical lens design. However, the anti-fogging properties of these masks generally suffer from problems such as reliance on external power sources, high maintenance costs, poor reliability, or limited lifespan. Currently, the mainstream solutions include the following:

[0004] (1) Anti-fog coating technology: A hydrophilic or hydrophobic coating, such as a silicon-based or fluorine-based compound coating, is applied to the lens surface. These coatings are initially effective, allowing water vapor to form a thin film instead of droplets, but they are easily damaged by wiping, contamination, or prolonged use. In the high-dust, high-humidity environment of mines, coating wear is accelerated, and the lifespan is often less than a month, requiring frequent lens replacements, increasing maintenance costs and downtime. In addition, coating peeling may introduce foreign objects, affecting the cleanliness of the respiratory system.

[0005] (2) Electric heating anti-fog: Heating the lens via a built-in heating wire or transparent conductive film (such as ITO film) requires an additional power supply system, such as a battery or external power source. This not only increases the weight of the equipment (usually by 10% to 20%) and energy consumption (0.5 to 1W per hour), but also poses electrical safety hazards, such as short circuits or leakage, making it particularly unsuitable for intrinsically safe mining equipment. In explosive gas environments, electrical components may ignite sparks, violating coal mine safety regulations (such as AQ standards). Furthermore, uneven heating may cause thermal stress deformation of the lens, affecting optical performance.

[0006] (3) Chemical anti-fogging agent application: Using sprays or wipes, such as surfactants or glycerin-based compounds, requires frequent manual reapplication. In high humidity and dusty environments, the effect is unstable and the operation is cumbersome. During mine operations, rescue team members have difficulty maintaining the anti-fogging agent on-site, and the agent may react with respirable gases to produce harmful volatile substances, threatening health. Long-term use may also corrode lens materials and reduce light transmittance.

[0007] (4) Ventilation and fog prevention: Moisture can be dispersed by increasing the airflow speed inside the mask, but this often requires increasing the oxygen supply, wasting oxygen resources, and may introduce cold air from the outside, further reducing the internal temperature. Another auxiliary method is to use desiccants to absorb moisture, but desiccants need to be replaced after they are saturated, and are not suitable for long-term continuous operation.

[0008] These existing technologies share several drawbacks: first, they rely on external assistance and cannot achieve self-sustaining operation; second, they have low integration with the respirator itself, increasing system complexity; and third, they have poor adaptability, with a high failure rate under extreme mine conditions (such as low temperature, high humidity, and vibration). According to relevant statistics, approximately 15% to 20% of vision-related problems in mine rescue accidents stem from lens fogging, directly impacting rescue efficiency and safety. Internationally, standards such as the EU EN standard and the US NIOSH standard have strict requirements for respirator visual clarity (transmittance ≥85%, field of view ≥70°), but existing anti-fogging solutions are difficult to meet these requirements long-term.

[0009] Furthermore, existing double-lens applications are mainly found in civilian face shields, such as ski goggles or military goggles. These designs rely on external airflow or heating elements and are not suitable for closed-loop positive pressure breathing apparatus used in mining. Mining environments require equipment to be inherently safe, independent of external energy sources, and deeply integrated with the oxygen circulation system to avoid oxygen leakage or waste.

[0010] Therefore, there is an urgent need for a highly efficient anti-fog structure that does not require an external power source, does not rely on consumable materials, can be deeply integrated with the positive pressure breathing apparatus body, and has self-sustaining capabilities, so as to fundamentally solve the problem of fogging of the lenses of mining breathing apparatus. Summary of the Invention

[0011] In view of this, the purpose of this invention is to solve the technical problem of easy fogging of the lens of the full-face mask of the existing positive pressure oxygen respirator for mining. It provides a method and structure for anti-fogging with double-layer lenses for the full-face mask of the positive pressure oxygen respirator for mining. This method and structure utilize the heat energy generated during the operation of the respirator to construct an integrated anti-fogging system of "double-layer lens + interlayer gas heating and insulation + closed-loop circulation integration + positive pressure leakage prevention," ensuring that the temperature of the inner lens is always higher than the dew point temperature, thus blocking the formation of fog droplets at the source. It ensures that the solution does not affect the normal oxygen supply and breathing cycle of the positive pressure respirator, while meeting safety indicators such as the light transmittance and field of vision of the full-face mask. It solves the problems of fogging of existing single-layer masks and the complexity or poor effectiveness of existing anti-fogging methods, achieving the goal of long-term, energy-saving, safe, maintenance-free anti-fogging and clear vision in the underground mining environment.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] A mine-use positive pressure oxygen respirator features a full-face mask with double-layered lenses and an anti-fog structure. The mask includes an outer lens, an inner lens, a sealing frame, an upper clamp, and a lower clamp. The outer and inner lenses are fixed and arranged parallel to each other by the sealing frame, forming a double-layered lens interlayer. The sealing frame, made of flexible material, surrounds the edges of the outer and inner lenses and is secured to them by the upper and lower clamps with an interference fit, providing sealing and structural support. The sidewall of the double-layered lens interlayer is provided with an inlet insulated pipe and an outlet. The double-layered lens interlayer is connected to a spiral pipe within the heat exchange chamber of the respirator's purification canister via the inlet insulated pipe. The spiral pipe receives branch oxygen output from the respirator's pressure reducer and absorbs the reaction heat of the CO2 absorbent in the purification canister, causing the oxygen to heat up before entering the double-layered lens interlayer and heating the inner lens. The oxygen discharged from the double-layered lens interlayer enters the mask cavity through the outlet and merges into the respirator's closed-loop circulation system.

[0014] Furthermore, the inner side of the outer lens and the outer side of the inner lens are coated with an anti-reflective film.

[0015] Furthermore, the antireflective coating is a MgF2 film with a thickness of 80–120 nm, and the light transmittance of a single-layer coated lens is ≥93%.

[0016] Furthermore, the interlayer spacing of the double-layer lens is ≤3mm.

[0017] Furthermore, the outer and inner lenses are made of optical-grade polycarbonate material with a thickness of 1.5–2.5 mm.

[0018] Furthermore, the air intake insulation pipe is connected to the upper inlet of the double-layer lens interlayer, and a guide plate is provided at the inlet to achieve uniform airflow distribution.

[0019] Furthermore, the guide plate has a fan-shaped structure and is fixed to the inner lens by ultrasonic welding, so that the airflow is evenly distributed to both sides.

[0020] Furthermore, the air outlet is located below the double-layer lens interlayer, and the diameter of the air outlet is smaller than the diameter of the air inlet to maintain positive pressure inside the interlayer.

[0021] Furthermore, the diameter of the air inlet is 3-5 mm, and the diameter of the air outlet is 1.5-2.5 mm.

[0022] Furthermore, the spiral pipe is made of copper and is installed inside the heat exchange chamber of the purification tank to efficiently conduct the reaction heat of the CO2 absorbent.

[0023] Furthermore, it also includes a cooler located on the main oxygen supply of the respirator, which is used to initially cool the main oxygen supply of the respirator so that the anti-fogging effect is not affected when the mask cavity temperature is low.

[0024] A method for preventing fogging of a full-face mask with double-layer lenses in a positive pressure oxygen respirator for mining is provided. Based on the aforementioned anti-fogging structure, branch oxygen is output from the respirator pressure reducer and enters a spiral pipe in the heat exchange chamber of the clean tank. This oxygen absorbs the reaction heat of the CO2 absorbent, causing the oxygen to heat up. The heated oxygen then enters the double-layer lens interlayer through an insulated inlet pipe, convectively heating the inner lens to a temperature higher than the dew point. The oxygen in the double-layer lens interlayer enters the mask cavity through the outlet, participating in the respirator's closed-loop breathing cycle.

[0025] Furthermore, the oxygen in the branch line accounts for 20% to 30% of the total output flow of the pressure reducer.

[0026] Furthermore, the oxygen in the branch circuit is heated to above 35°C.

[0027] Furthermore, the size difference between the air inlet and outlet on the mask maintains a slight positive pressure within the double-layer lens interlayer, preventing cold air from seeping in and condensation from flowing back in.

[0028] Furthermore, the airflow is guided to be evenly distributed by the air inlet of the double-layer lens interlayer, and the gas replacement in the double-layer lens interlayer is controlled to be 5 to 10 times per minute, and the natural rising characteristics of hot air are used to promote moisture migration.

[0029] The beneficial effects of this invention are as follows:

[0030] The anti-fogging method and structure of the full-face mask with double-layer lenses for positive pressure oxygen respirators used in mines provided by this invention have significant beneficial effects:

[0031] First, its long-lasting anti-fog performance is outstanding: the oxygen interlayer formed by the double-layer lens acts as a heat insulation buffer, and continuously heats the inner lens through convection heat transfer, ensuring that its surface temperature remains above the moisture dew point temperature, thus preventing condensation and fogging at the source. Compared to traditional anti-fog coatings or chemical agents, this method does not rely on consumable materials, utilizing the dry heat gas generated by the respirator itself to achieve continuous anti-fog operation. This meets the needs of continuous rescue operations in mines for more than 4 hours, avoids downtime losses caused by frequent maintenance, and improves operational efficiency.

[0032] Secondly, it boasts strong safety and compatibility: Anti-fogging oxygen is fully integrated into the respirator's closed-loop circulation system, preventing oxygen waste and improving resource utilization. The diversion flow rate is controlled at 20%–30%, ensuring no impact on oxygen supply safety. A positive pressure leak-proof mechanism ensures a slightly positive pressure inside the mask compared to the outside, preventing cold air infiltration and condensate backflow, enhancing overall sealing reliability, meeting intrinsic safety requirements for mining applications, and reducing the risk of explosion.

[0033] Third, it boasts a long lifespan and easy maintenance: avoiding issues like coating wear or heating element failure, the double-layered lenses have a lifespan consistent with the main mask body, typically exceeding 5 years. The structural design requires no maintenance, eliminating the need for external power or consumables, thus reducing the equipment's lifecycle cost. Its anti-fog performance remains stable in environments ranging from -10℃ to 40℃, resolving the "low-temperature failure" problem of traditional solutions.

[0034] Fourth, clear vision and excellent optical performance: The mask features a double-layer PC lens and anti-reflective coating, resulting in a total light transmittance of ≥86%. It boasts strong scratch resistance, unobstructed interlayer design, and a field of view of ≥70°, meeting international safety standards. The anti-reflective coating reduces reflection and improves image clarity, helping rescue team members identify details in low-light mines.

[0035] Fifth, it has wide environmental adaptability: it can operate stably under extreme mining conditions, including high humidity, dust, and vibration environments. The internal heat source utilization mechanism enables the system to adapt; as usage time increases, the heat of CO2 absorption reaction increases, further enhancing the anti-fogging effect. Compared to electric heating solutions, this invention is significantly energy-efficient, consumes no additional energy, and aligns with the concept of green mining.

[0036] Furthermore, this invention is easily integrated into existing equipment, such as the HYZ4 respirator, and can be implemented through simple modifications, resulting in low promotion costs. Overall, this invention addresses the root cause of the technical problem by constructing an integrated system, which not only solves the lens fogging problem but also improves the overall performance of the respirator, promoting the innovative development of mining protective equipment.

[0037] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0039] Figure 1 This is a cross-sectional view of the face mask in this invention.

[0040] Figure 2 This is a schematic diagram of the inner side of the face mask in this invention.

[0041] Figure 3 This is a schematic diagram of the outer side of the mask in this invention.

[0042] Figure 4 This is a schematic diagram of the basic structure of an oxygen respirator.

[0043] Figure 5 This is a schematic diagram illustrating the principle of an oxygen respirator.

[0044] Figure 6 This is a schematic diagram illustrating the anti-fog principle of the face mask.

[0045] Reference numerals: 1-Mask; 20-Outer lens; 21-Inner lens; 22-First antireflective coating; 23-Second antireflective coating; 24-Lower clamp; 25-Sealing frame; 26-Upper clamp; 27-Insulated air inlet pipe; 28-Blower plate; 29-Outlet; 2-Inhalation hose; 3-Pressure roller; 4-Cooler; 5-Monitoring device; 6-Pressure reducer; 7-Cylinder valve; 8-Lower outer shell; 9-Upper outer shell; 10-Oxygen cylinder; 11-Airbag; 12-Positive pressure spring; 13-Exhaust valve; 14-Self-compensating valve; 15-Cleaning canister; 16-Pull rod; 17-Exhalation hose; 18-Electronic alarm; 19-Breathing three-way valve. Detailed Implementation

[0046] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0047] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0048] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0049] Example 1

[0050] The following uses the HYZ4 positive pressure oxygen respirator as an example, combined with the attached... Figures 1-6 The technical solution, assembly process, and usage process of the present invention are described in detail.

[0051] (I) Technical Solution

[0052] The anti-fog structure of the present invention includes a face shield 1, which is composed of an outer lens 20, an inner lens 21, a sealing frame 25, an upper clamp 26, and a lower clamp 24. The outer lens 20 and the inner lens 21 are made of optical-grade polycarbonate (PC) material with a thickness of 1.5 to 2.5 mm (preferably 2 mm). They are fixed and arranged in parallel by the sealing frame 25 to form a double-layer lens sandwich with a spacing of ≤3 mm. The sealing frame 25 is made of flexible rubber and surrounds the edges of the outer lens 20 and the inner lens 21, providing a seal and flexible cushioning to prevent the lenses from deforming under force. The upper clamp 26 and the lower clamp 24 are fastened by interference fit with buckles and screws to fix the lenses and ensure the airtightness of the sandwich, preventing gas leakage or the infiltration of cold air from the outside.

[0053] The sidewalls of the double-layer lens interlayer are equipped with an insulated air inlet pipe 27 and an air outlet 29. The insulated air inlet pipe 27 connects to the upper inlet of the interlayer, and a fan-shaped guide plate 28 is installed at the inlet and fixed to the inner lens 21 by ultrasonic welding, so that the oxygen entering the interlayer is evenly distributed to both sides, enhancing the convective heat transfer effect. The air outlet 29 is located below the interlayer, with a diameter of 1.5-2.5 mm (preferably 2 mm), which is 3-5 mm (preferably 4 mm) smaller than the diameter of the air inlet, in order to maintain a slight positive pressure inside the interlayer and prevent cold air from seeping in and condensate from flowing back in.

[0054] The inner side of the outer lens 20 and the outer side of the inner lens 21 are coated with a first antireflective film 22 and a second antireflective film 23, respectively. The film is made of MgF2 and has a thickness of 80-120nm (preferably 100nm). After coating, the light transmittance of a single lens is ≥93% and the total light transmittance of the mask is ≥86%, so as to improve the clarity of vision and anti-reflection performance and meet the visual needs in the low light environment of the mine.

[0055] The insulated air intake duct 27 is connected to the spiral duct inside the heat exchange chamber of the cleanroom 15 via a pre-drilled hole in the sealing frame 25. The spiral duct is made of copper and efficiently conducts the heat of reaction of the CO2 absorbent, heating the branch oxygen before introducing it into the interlayer to heat the inner lens 21. The oxygen discharged from the interlayer enters the mask cavity through the outlet 29 and merges into the respirator's closed-loop circulation system, ensuring that oxygen resources are not wasted.

[0056] The main oxygen path of the respirator is equipped with a cooler 4, which is used to initially cool the main oxygen, reduce the temperature of the mask cavity, and ensure stable anti-fogging performance in low-temperature environments. The entire structure works in conjunction with the oxygen cylinder 10, cylinder valve 7, pressure reducer 6, clean canister 15, air bag 11, inhalation hose 2, expiratory hose 17, breathing three-way valve 19 and other components of the HYZ4 respirator to form a closed-loop circulation system.

[0057] The anti-fog method of the present invention is based on the above structure and includes the following steps:

[0058] 1. Oxygen is output from the branch line of pressure reducer 6, accounting for 20% to 30% of the total output flow, to ensure that the main oxygen supply is not affected.

[0059] 2. The oxygen from the branch line enters the spiral copper tube in the heat exchange chamber of the purification tank 15, absorbs the heat of reaction of the CO2 absorbent, and rises to above 35°C.

[0060] 3. Heated oxygen enters the inlet above the double-layer lens interlayer through the insulated air intake pipe 27, and is guided by the fan-shaped guide plate 28 to be evenly distributed along the curved surface of the inner lens 21 for convective heat exchange, so that the temperature of the inner lens 21 is higher than the dew point, preventing condensation and fogging.

[0061] 4. The interlayer oxygen enters the mask cavity through the lower outlet 29, mixes with the main oxygen, and participates in the closed-loop breathing cycle.

[0062] The size difference between the air inlet (4mm in diameter) and the air outlet 29 (2mm in diameter) maintains a slight positive pressure within the interlayer, preventing the infiltration of cold air and the backflow of condensate. Simultaneously, utilizing the natural upward movement of hot air, combined with the top-inlet, bottom-outlet layout and the baffle plate 28, the interlayer gas is replaced 5-10 times per minute, driving trace amounts of moisture towards the air outlet 29 to prevent liquid accumulation in the interlayer.

[0063] (II) Assembly Process

[0064] 1. Lens processing: Optical-grade polycarbonate (PC) material is used to process an outer lens 20 and an inner lens 21 with a thickness of 2mm. A first anti-reflective coating 22 is deposited on the inner side of the outer lens 20, and a second anti-reflective coating 23 is deposited on the outer side of the inner lens 21. Both are MgF2 films with a thickness of 100nm. After coating, the light transmittance of a single-layer lens is tested to be ≥93%, ensuring high light transmittance and anti-reflective performance.

[0065] 2. Inner lens modification: An air inlet with a diameter of 4mm is opened above the interlayer sidewall of the inner lens 21, and an air outlet with a diameter of 2mm is opened below it. An air insulated pipe 27 and a fan-shaped guide plate 28 are installed at the air inlet. The guide plate 28 is fixed to the inner lens 21 by ultrasonic welding to ensure uniform oxygen distribution in the branch.

[0066] 3. Double-layer lens assembly: The inner lens 21 is installed into a flexible rubber sealing frame 25, which surrounds the edges of the outer lens 20 and the inner lens 21. Silicone grease is applied to the edges to enhance the sealing. The outer lens 20 is then stacked on top of the inner lens, so that the two lenses are arranged in parallel with a gap of ≤3mm. An interference fit is achieved through the upper clamp 26 and the lower clamp 24, and the lenses are fastened with buckles and screws to provide sealing and structural support.

[0067] 4. System Connection: Secure the oxygen cylinder 10, cylinder valve 7, pressure reducer 6, cleanroom canister 15, cooler 4, air bag 11, inhalation hose 2, exhalation hose 17, breathing three-way valve 19, positive pressure spring 12, exhaust valve 13, self-compensating valve 14, monitoring device 5, electronic alarm 18, pull rod 16, pressure wheel 3, lower outer shell 8, and upper outer shell 9 sequentially to the designated positions on the HYZ4 respirator and connect them. Connect one end of the shunt pipe to the pressure reducer 6 and the other end to the inlet of the spiral copper tube in the heat exchange chamber of the cleanroom canister 15; connect the inlet insulated pipe 27 to the spiral copper tube outlet through the pre-drilled hole in the sealing frame 25. The cooler 4 is placed in the main oxygen path to reduce the initial breathing gas temperature. Finally, cover the upper outer shell 9 and connect the breathing three-way valve 19 to the mask 1.

[0068] (III) Usage Process

[0069] 1. Start the equipment: Wear the HYZ4 positive pressure oxygen respirator correctly, adjust the mask 1 to ensure a tight seal, and open the valve 7 of the oxygen cylinder 10. The high-pressure oxygen is reduced in pressure by the pressure reducer 6 and divided into main oxygen and branch oxygen. The branch oxygen accounts for 20% to 30% of the total output flow. The main oxygen is cooled by the cooler 4 and then enters the mask cavity through the inhalation hose 2.

[0070] 2. Anti-fog operation: Branch oxygen enters the spiral copper tube of the purification tank 15, absorbs the heat of reaction from the CO2 absorbent, and rises to above 35°C; it then enters the inlet above the double-layer lens interlayer through the insulated intake pipe 27, is evenly distributed by the fan-shaped guide plate 28, and flows along the curved surface of the inner lens 21, heating the inner lens 21 to above the dew point; the interlayer oxygen enters the mask cavity through the lower outlet 29, mixes with the main oxygen, and participates in the closed-loop circulation. The size difference between the inlet and outlet 29 maintains a slight positive pressure within the interlayer, preventing cold air from seeping in. The guide plate 28 guides the airflow, replacing it 5-10 times per minute, promoting moisture migration and preventing liquid accumulation.

[0071] 3. Breathing Cycle: During inhalation, the inhalation valve of the breathing three-way valve 19 opens and the exhalation valve closes. The main oxygen enters the mask cavity through the inhalation hose 2 and mixes with the branch oxygen discharged from the interlayer. During exhalation, the exhalation valve of the breathing three-way valve 19 opens and the inhalation valve closes. The exhaled gas enters the purification canister 15 through the exhalation hose 17 to purify CO2 before returning to the air bag 11, where it mixes with the main oxygen in the pressure reducer 6, completing the closed-loop cycle.

[0072] 4. Positive pressure and replenishment regulation: When the oxygen supply exceeds the oxygen consumption, the pressure in the airbag 11 increases to 400Pa~700Pa, and the exhaust valve 13 automatically vents, maintaining a positive pressure state. When the oxygen supply is insufficient, the self-replenishing valve 14 automatically opens when the pressure in the airbag 11 is 10Pa~245Pa, or the oxygen supply can be increased by manually pressing the replenishment button to ensure positive pressure in the respiratory system.

[0073] This embodiment achieves long-lasting anti-fogging through a double-layer lens sandwich structure (outer lens 20, inner lens 21, sealing frame 25, upper clamp 26, lower clamp 24), branch oxygen heating (cleaning tank spiral copper pipe, inlet insulated pipe 27), positive pressure mechanism (size difference between air inlet and outlet 29), airflow replacement (guide plate 28, 5-10 times / minute), and closed-loop circulation integration. The anti-reflective coatings on the outer lens 20 and inner lens 21 improve light transmittance, the cooler 4 stabilizes the initial breathing gas temperature, and the entire system is compatible with the HYZ4 type respirator, meeting the requirements for continuous operation of more than 4 hours in a mining environment.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A mine-used positive pressure oxygen breathing apparatus full face mask double-layer lens anti-fog structure, characterized in that, The mask comprises an outer lens, an inner lens, a sealing frame, an upper clamp and a lower clamp; the outer lens and the inner lens are fixed and arranged in parallel by the sealing frame to form a double-layer lens interlayer; the sealing frame is made of flexible material and surrounds the edges of the outer lens and the inner lens, and is in interference fit with the outer lens and the inner lens and is fastened by the upper clamp and the lower clamp to provide sealing and structural support; the sidewall of the double-layer lens interlayer is provided with an air inlet heat insulation pipeline and an air outlet, and the double-layer lens interlayer is connected with a spiral pipeline in a heat exchange cavity in a breathing apparatus clean tank through the air inlet heat insulation pipeline; the spiral pipeline receives branch oxygen output by a breathing apparatus pressure reducer, absorbs reaction heat of a CO2 absorbent in the clean tank, and makes the oxygen enter the double-layer lens interlayer after being warmed, so as to heat the inner lens; the oxygen discharged from the double-layer lens interlayer enters a mask cavity through the air outlet and flows into a breathing apparatus closed circuit system.

2. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, The inner side of the outer lens and the outer side of the inner lens are coated with an anti-reflection film.

3. The double-layer lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 2, characterized in that, The anti-reflection film is an MgF2 film with a thickness of 80-120 nm, and the single-layer coated lens has a light transmittance of ≥93%.

4. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, The distance between the double-layer lens interlayers is ≤3 mm.

5. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, The outer lens and the inner lens are made of optical-grade polycarbonate material with a thickness of 1.5-2.5 mm.

6. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, The air inlet heat insulation pipeline is connected to an upper inlet of the double-layer lens interlayer, and a guide plate is arranged at the inlet to achieve uniform distribution of airflow.

7. The mine positive pressure oxygen respirator full face mask double layer lens anti-fog structure according to claim 6, characterized in that, The guide plate is in a fan-shaped structure and is fixed on the inner lens by ultrasonic welding to make the airflow uniformly distributed to both sides.

8. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, The air outlet is located below the double-layer lens interlayer, and the diameter of the air outlet is smaller than that of the air inlet to maintain a positive pressure in the interlayer.

9. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, The diameter of the air inlet is 3-5 mm, and the diameter of the air outlet is 1.5-2.5 mm.

10. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, The spiral pipeline is made of copper and is arranged in the heat exchange cavity of the clean tank to efficiently conduct the reaction heat of the CO2 absorbent.

11. The dual lens anti-fog structure of the positive pressure oxygen breathing apparatus overall cover for mine according to claim 1, characterized in that, A cooler is arranged on the main oxygen pipeline of the breathing apparatus, and the cooler is used to initially cool the main oxygen pipeline of the breathing apparatus to prevent the anti-fog effect from being affected when the temperature of the mask cavity is low.

12. A method for preventing fogging of the double-layer lens of the full facepiece of a mine positive pressure oxygen breathing apparatus based on the anti-fogging structure of claim 1, characterized in that: Branch oxygen is output from the breathing apparatus pressure reducer, enters the spiral pipeline in the heat exchange cavity of the clean tank, absorbs the reaction heat of the CO2 absorbent, and is warmed; the warmed oxygen enters the double-layer lens interlayer through the air inlet heat insulation pipeline, convectively heats the inner lens, and makes the temperature of the inner lens higher than the dew point; the oxygen in the double-layer lens interlayer enters the mask cavity through the air outlet to participate in the breathing closed circuit of the breathing apparatus.

13. The anti-fog method according to claim 12, characterized by, The branch oxygen accounts for 20%-30% of the total output flow of the pressure reducer.

14. The anti-fog method according to claim 12, characterized by, The branch oxygen is warmed to above 35°C.

15. The anti-fog method according to claim 12, characterized by, The size difference between the air inlet and the air outlet of the mask maintains a slight positive pressure in the double-layer lens interlayer, prevents external cold air from penetrating and condensate water from flowing back, and controls the gas replacement in the double-layer lens interlayer to 5-10 times per minute.

16. The anti-fog method according to claim 12, wherein The guide plate arranged at the air inlet of the double-layer lens interlayer guides the airflow to be uniformly distributed, and the gas replacement in the double-layer lens interlayer is controlled to 5-10 times per minute to promote water migration by using the natural upward characteristic of hot air.

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